Environmental Engineering Reference
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into 50 mL LB medium containing E. coli DH5ʱ and B. subtilis inoculums
separately, leaving one as a control to track the normal microbial growth and
shaken at 180 rpm at 37 ± 2 °C. Optical density measurement at 600 nm indicates
the bacterial growth interacting with nanoparticle and the viability was determined
from a plot of the log of the optical density versus time.
Uptake Studies of Chromium (VI) in Batch Process
Cr(VI) uptake studies have been performed in a batch process in which glutathion-
ated iron nanoparticles were evaluated for chromium(VI) removal effi ciency.
Adsorption studies were performed by adding 25 mL of the solution in 100 mL
Erlenmeyer fl ask containing different concentration (0.1-1.0)
g/mL of potassium
di-chromate to 100
g/mL of GSH-loaded iron nanoparticles sepa-
rately. The pH of the solutions and iron nanoparticles were separately adjusted at
7.0. Flasks were placed on a rotary shaker and shaken at 120 rpm at 37 ± 2 °C. After
desired incubation (24 h), Cr(VI) loaded nanoparticles were separated with mag-
netic decantation and the supernatant has been analyzed for Cr(VI) concentration.
g/mL and 200
Chromium(VI) Analysis
Cr(VI) removal was measured as the decrease of chromate using Cr(VI) specifi c colo-
rimetric reagent S-diphenylcarbazide (DPCZ). About 1 mL of 0.05 % DPCZ (w/v in
acetone) was added to 1 mL of water sample and additionally 3 mL of 0.16 M sulfuric
acid was poured for minimizing the deterioration (Urone 1955 ). A purple complex was
formed due to the reaction of DPCZ with chromate. The absorbance was taken imme-
diately at 540 nm in a spectrophotometer. Quantity of Cr(VI) was measured obtaining
the calibration curve using potassium di-chromate (K 2 Cr 2 O 7 ) solution as standard.
Effect of pH on Cr(VI) Adsorption
Aqueous chromium solution (2
g/mL) was adjusted to the required pH (3, 11)
using 0.1 N HCl or 0.1 N NaOH. Flasks were shaken with 120 rpm at 37 ± 2 °C for
required incubation time (24 h).
Absorption Studies of Malachite Green (MG)
MG uptake studies were performed in a batch process according to Afkhami et al.
( 2010 ) with some modifi cation. Effect of pH has been studied with SDS iron
nanoparticles as absorbent. Adsorption studies were performed by adding 25 mL of
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